1. Field of the Invention
This invention relates to a method of and apparatus for opening score lines in a fracturable material, and more particularly, to opening score lines in a glass sheet advancing along or stationary in an article movement path by displacing a bending moment across the glass sheet in a direction transverse to the score lines and the article movement path.
2. Discussion of the Prior Art
In U.S. Pat. Nos. 2,504,655; 3,259,286 and 3,592,370 there is taught the opening of score lines in a moving glass sheet. In general, score opening devices are mounted along an article movement path to apply a bending moment to a score line as the glass sheet advances past the devices.
Although opening score lines taught in the above-identified patents are acceptable, there are drawbacks. For example, a plurality of score lines on the glass have to be parallel to one another and to the article movement path. This is because the score opening devices are stationary and aligned with score lines of a given glass sheet.
If the score lines are not parallel to the glass travel path, the score line will not completely pass between the score opening device. When this occurs only a portion of the score line is opened. Further, the glass sheet has to maintain its orientation as it is conveyed past the score opening devices. If the glass sheet shifts as it advances toward the score opening devices, the score line passes along side rather than between the score opening device. As can be appreciated, providing equipment to maintain the orientation of the glass sheet with respect to the score opening devices is expensive. Still further, when the position of the score lines on the glass sheet is changed, the score opening devices have to reposition so that the score line passes between the devices.
Also taught in the prior art, e.g., in U.S. Pat. Nos. 1,997,402 and 3,181,757 is the opening of score lines on a glass sheet that are transverse to the article movement path. In general, a score opening device is mounted in the article movement path to open the score lines. The score opening device may be a pair of spaced cylindrical rolls having their axial center transverse to the article movement path or a pair of upper spaced rotatably mounted wheels and a pair of bottom spaced rotatably mounted wheels.
This prior art technique of opening score lines has limitations, one of which is versatility. More particularly, the score opening technique is not suitable for processing glass sheets having pairs of intersecting lateral and longitudinal score lines because the longitudinal score lines can open during the opening of the lateral score lines. For example, foreign particles, e.g., glass chips trapped between the scoring devices and glass sheets cooperate with the weight of the glass to apply a bending moment to the longitudinal score lines opening same.
Another limitation is the dependency on the type of conveyor used and the distance between lateral score lines. If the distance between lateral score lines is less than the distance between conveyor roller surfaces, the severed glass section will fall between the rollers. This drawback can be overcome by using a belt conveyor. However, when the glass sheet has lateral and longitudinal score lines, additional conveying equipment has to be used to reorientate the glass sections to open the longitudinal score lines.
In U.S. Pat. No. 3,268,135 there is taught another score opening device. In general, a glass sheet is advanced over conveyor rollers that are flexed upward to open longitudinal score lines to provide glass sections. The glass sections, while in the raised position, engaged skewed rollers to separate adjacent sides of the glass sections.
The drawback of the score opening technique of U.S. Pat. No. 3,268,135 is the need for precision alignment of the equipment. If the longitudinal score lines in the glass sheet are opened and the skewed wheels do not engage the glass sections, adjacent edges of the glass sections contact one another when the conveyors are flexed from the arched position to the horizontal position. When the edges of the glass sections contact one another chipping and craking of the edges result.
It would be advantageous therefore to provide a score opening device and method of opening score lines that do not have the limitation and drawbacks of the prior art.